Wireless communication over a transducer device

ABSTRACT

One aspect of the present invention is generally directed towards a system and method of tuning a transducer for transmitting and receiving a wireless signal. In an illustrative embodiment, a single transducer is coupled to a first or second circuit for either transmitting or receiving, respectively. Generally, electrical characteristics of the first circuit are adjusted to increase a magnetic field generated by the transducer. Conversely, electrical characteristics of the second circuit are adjusted to increase a signal generated by the transducer for receiving a magnetic field. Accordingly, a single transducer device can be tuned for either transmitting or receiving a corresponding wireless signal.

RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.10/004,989, filed on Dec. 3, 2001, which is a Continuation-in-part ofU.S. application Ser. No. 09/942,372, filed on Aug. 29, 2001, nowabandoned, which claims the benefit of U.S. Provisional Application No.60/296,229, filed on Jun. 6, 2001 and U.S. Provisional Application No.60/276,398, filed on Mar. 16, 2001. The entire teachings of the aboveapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Inductive antenna devices have been incorporated in transceivers totransmit and receive wireless signals for quite some time. In a typicalapplication, a transceiver device supporting bi-directionalcommunication includes two specifically tuned antennas, one of which istuned for transmitting while the other is tuned for receiving.

Unlike RF (Radio Frequency) antennas, inductive antennas are oftenindependently tuned for more efficiently transmitting or receivingwireless signals. For example, inductive antennas used for transmittingare generally tuned so they effectively have a low impedance.Conversely, inductive antennas used for receiving are typically tuned sothey effectively have a high impedance. Most inductive systemssupporting two-way communications include separate antenna devices, eachof which is tuned for either transmitting or receiving at a particularcarrier frequency.

SUMMARY OF THE INVENTION

Recent advancements in integrated circuit technology render it possibleto reduce an overall size of wireless transceiver devices. Additionally,the size and weight of power sources for powering corresponding wirelessdevices has been reduced to support increased portability. That is,wireless transceiver devices are now smaller than ever before. As aresult, a relative size and weight associated with the use of individualantennas for transmitting and receiving can be prohibitive due to spacerestrictions in certain wireless applications.

It would be an advancement in the art to reduce the power, cost, sizeand weight of a transceiver system such as a transducer and relatedcircuitry for transmitting and receiving wireless signals based oninductive coupling.

One aspect of the present invention is generally directed towards asystem and method of tuning a transducer for transceiving, i.e.,transmitting or receiving, wireless signals. In an illustrativeembodiment, a single transducer is coupled to a circuit for eithertransmitting or receiving. Generally, electrical characteristics of thecircuit can be adjusted to increase a magnetic field generated by thetransducer. Characteristics of the circuit also can be adjusted forreceiving a magnetic field. Accordingly, a single transducer device canbe tuned for either transmitting or receiving a wireless signal.

In one application, the circuit to which the transducer is coupled isbroken into two components such as first and second circuits. Thetransducer can be coupled to and tuned by the first circuit fortransmitting, while the transducer can be coupled to and tuned by thesecond circuit for receiving. Characteristics of the first and secondcircuits can be adjusted using passive circuit components such ascapacitors, inductors and resistors. Such circuit components aretypically inexpensive and can be easily mounted to a circuit board.Further, the first and second circuits can include active circuits fortuning the transducer for transmitting or receiving.

In a specific application, a capacitance of the first circuit can beadjusted to reduce an effective impedance of the transducer fortransmitting a wireless signal. Also, a capacitance of the secondcircuit can be adjusted to increase an effective impedance of thetransducer for receiving a wireless signal. Accordingly, a singletransducer can be switched or time-multiplexed between the first andsecond circuits to support bidirectional communication with atransceiver device at a remote location. By adjusting the electricalcharacteristics of a corresponding circuit, higher coupling efficiencycan be achieved between the tuned transducer and a remote transmitter orreceiver.

The first and second circuits can be adjusted for transmitting andreceiving at different carrier frequencies. For example, a reactance orimpedance of the first circuit can be adjusted for transmitting amagnetically encoded signal at a first carrier frequency whilecharacteristics of the second circuit can be adjusted to receive amagnetically encoded signal at a second carrier frequency.

Further, the first or second circuit can be adjusted for respectivelytransmitting or receiving over the transducer at different frequenciesduring different time intervals. More specifically, the transducer andfirst circuit can be adjusted to transmit at a first carrier frequencyfor a first time interval, and the transducer and first circuit can beadjusted or tuned to transmit at a second carrier frequency duringanother time interval. Also, the transducer can be adjusted to receiveon two different carrier frequencies during two different time intervalsby adjusting the second circuit when coupled to the transducer. Thus, asingle transducer can be dynamically tuned in the field to transmit atmultiple carrier frequencies and receive at multiple carrierfrequencies.

One method of tuning the transducer for transmitting involves disposingan inductive element in the second circuit. Preferably, the inductiveelement has an inductance approximately matching that of the transducer.In other words, a portion of circuitry used for tuning the transducerfor transmitting can be nullified by matching an inductive element inthe second circuit with a portion of the first circuit.

The second circuit optionally includes at least a portion of the firstcircuit or can be coupled to the first circuit. For example, certaincomponents such as a switch can be disposed for coupling a transmitterto the first circuit and transducer. Another switch can be positioned tocouple at least a portion of the first circuit with the second circuit.

Accordingly, the second circuit can be coupled to a portion of the firstcircuit for receiving a wireless signal over the transducer.

To support increased magnetic coupling efficiency, the first circuit canbe used to serially tune the transducer for transmitting and the secondcircuit can be used to parallel tune the transducer for receiving. Aspreviously discussed, the transducer generally is tuned to effectivelyhave a high impedance for receiving and a low impedance fortransmitting.

Another aspect of the present invention is directed towards a method andapparatus for supporting communication via magnetic coupling. Generally,the method involves switching to select either transmitting or receivingover a transducer. A first circuit effectively tunes the transducer to alow impedance device for generating a magnetic field when a transmitteris switched to transmit over the transducer. A second circuiteffectively tunes the transducer be a high impedance for receiving amagnetic field when a receiver is switched to receive over thetransducer. Thus, a common transducer device can be tuned to transmit orreceive a magnetic field depending on whether the transducer is tuned tobe a high or low impedance device. The ability to select eithertransmitting or receiving over a single transducer is particularlyadvantageous in space restricted applications because at least oneotherwise necessary transducer can be eliminated.

While in a transmit mode, the transducer can be serially tuned byreducing an overall reactance or impedance of the first circuitincluding the transducer. This can be achieved by substantially matchingan inductance of the transducer with a capacitance of the first circuitso that the corresponding reactance of each component cancels ornullifies each other. Thus, a single transducer can be dynamically tunedto transmit a wireless signal.

Switching functionality can be employed to support coupling of atransmitter and first circuit to the transducer for transmitting.Likewise, switching functionality can be employed to support coupling areceiver to a second circuit and the transducer for receiving.

In a specific application, the transmitter driving the transducer andrelated circuit generates an output at one of two voltages. For example,the transmitter can be controlled to produce a series of high and lowvoltage outputs for a specified duration of time to drive thetransducer. The transducer in turn will generate a correspondingmagnetic field depending on the applied voltage.

A resistance can be disposed in series with the transducer to adjust a Q(quality or efficiency factor) of the circuit for transmitting andreceiving over a particular resonant frequency. Adjusting the Q of thecircuit has an effect on the bandwidth of data information that can betransmitted or received at a particular carrier frequency to which thetransducer is tuned.

The combined impedance of the first circuit and transducer can beadjusted or tuned for generating a maximal magnetic power output of thetransducer at a particular carrier frequency. For example,characteristics such as the impedance of certain components in the firstcircuit can be dynamically adjusted so that the transducer produces amaximal magnetic field at a particular carrier frequency. Accordingly,the battery life of a transceiver can be extended because a transducercan be adjusted for efficient use.

In certain applications, an impedance of both the first and secondcircuits can be adjusted for transmitting and receiving over asubstantially similar carrier frequency. Thus, a single transducer canbe used to transmit and receive over a common carrier frequency withoutinterfering with other wireless devices potentially using other carrierfrequencies in the wireless spectrum.

One technique for tuning the transducer involves adjusting a reactanceof the first and second circuit by selectively switching capacitors inparallel to increase or decrease a capacitance of a capacitor bank. Thistechnique of tuning can be used to select at which carrier frequency thetransducer is tuned to transmit or receive.

Although the first circuit can be adjusted to tune a particulartransducer, the transducer itself can be an adjustable element fortuning with a corresponding circuit. It is thus possible to adjust acombined impedance of the first circuit and transducer for transmittingor receiving via an adjustable transducer device.

One method of tuning a circuit for transmitting a maximal or increasedwireless signal from the transducer involves positioning a secondtransducer to receive at least a portion of a magnetic signaltransmitted from the first transducer. While driving a combination ofthe first circuit and transducer with the transmitter, a reactance ofthe first circuit can be adjusted to determine which setting of thefirst circuit produces a maximal signal at the receiving secondtransducer. In other words, feedback from a pickup or second transducercan be used to tune the transducer for transmitting. Likewise, thesecond transducer can generate a wireless signal while a receivingtransducer and related circuitry is adjusted to optimally receive thegenerated wireless signal.

Switching techniques according to the principles of the presentinvention enable a single transducer to transmit and receive based ontime division multiplexing. In a specific application, the transducersupports half duplex communication with a remote receiver. That is, thetransducer can transmit to a remote transceiver during specifiedintervals and receive from the remote transceiver during other timeintervals.

In yet another more specific application, a transmitter can be decoupledfrom the first circuit and transducer while at least a portion of thefirst circuit and transducer are coupled to the second circuit. Areactance of one or multiple components in the first circuit and areactance of one or multiple components in the second circuit can bepositioned to substantially cancel each other. For example, an inductorin the second circuit can be matched with the inductance of thetransducer or a capacitance of the first circuit to reduce a combinedimpedance or reactance of both circuits to tune the transducer forreceiving.

An electronic switch circuit can enable coupling and decoupling of thetransmitter from the first circuit and transducer. When decoupled, thetransmitter generally does not negatively affect the functionality ofthe transducer when set to a receiving mode since it is disconnected viaan open switch.

Instead of a single transducer, multiple transducers can be utilized fortransmitting and receiving. Each of the multiple transducers can beuniquely oriented so that a generated magnetic field can be coupled witha remote transceiver having an unknown orientation.

In one application incorporating multiple transducers, the first andsecond circuits are switched to receive over one of the multipletransducers. Alternatively, each transducer can have its own dedicatedfirst and second circuits for tuning the corresponding transducer fortransmitting and receiving. More specifically, dedicated circuitrycoupled to a corresponding transducer can be adjusted for transmittingor receiving at a particular carrier frequency as previously discussedfor a single transducer application.

To increase wireless coupling with a remote transceiver, the multipletransducers can be positioned so they are uniquely oriented with respectto each other. For example, three transducers can be positionedsubstantially orthogonal to each other. Consequently, at least one ofthe transducers typically can be used to communicate with a remotetarget transceiver regardless of its orientation with respect to themultiple transducers.

In yet another application including multiple transducers, the first andsecond circuits can be switched for transmitting on one of thetransducers while receiving on another transducer. If no signal isreceived from a remote transceiver device on a selected one of themultiple transducers, another transducer can be selected to receive amagnetic signal. The unique orientation of the multiple transducersensures that a magnetic signal can be received from at least one of thetransducers at all times.

When the multiple transducers are positioned near each other, circuitryfor tuning a particular transducer can be adjusted while one transduceris transmitting and one transducer is receiving. For example, a selectedtransducer in a group of multiple transducers can be tuned fortransmitting a signal while another transducer in the group and relatedcircuitry can be selected to receive the transmitted signal. Duringreception, characteristics of the transmitting transducer and relatedcircuit can be adjusted so that an increased signal is received at thereceiver. Similarly, the transducer and related circuitry selected toreceive the signal can be adjusted for optimal reception whiletransmitting on a different transducer. Generally, the intensity of areceived signal can be monitored to tune a circuit for optimallyreceiving or transmitting over a transducer.

Another aspect of the present invention is also directed towards anapparatus and method for supporting communication via inductivecoupling. Generally, one of multiple circuit paths can be selected foreither transmitting or receiving over a transducer. An overall impedanceof a first circuit path including the transducer can be reduced fortransmitting an inductive signal over the transducer. An overallimpedance of at least a portion of a second path can be reduced forreceiving an inductive signal over the transducer. Thus, a singletransducer can be used to transmit or receive depending on which ofmultiple circuit paths is switched for transmitting or receiving.

More specifically, when the transmitter is switched to transmit over thetransducer via the first circuit path, an overall impedance of the firstcircuit path including the transducer can be reduced by substantiallymatching a reactance of the transducer with circuit components disposedalong the first path. For example, an inductance of the transducer canbe cancelled via a capacitance switched into the first circuit path.Thus, the first circuit can have an impedance that is almost entirelyreal, i.e., there is little or no reactance in the first circuit path.Accordingly, the transducer can be tuned for efficiently generating awireless signal such a magnetic field for inductive communications.

Circuit components for adjusting an impedance of a circuit path caninclude passive elements such as resistors, inductors and capacitors.

The second circuit path can be coupled to the first circuit path via aserially disposed switch. Consequently, the second circuit path caneffectively include the first circuit path for receiving over thetransducer. During reception, a transmitter is optionally decoupled fromthe first circuit path so that it has a minimal effect oncharacteristics of the second circuit path.

The second circuit path also can be coupled to a receiver for receivingover the transducer, while at least a portion of a reactance along thesecond circuit path is reduced by substantially matching a reactance ofthe transducer with at least one circuit component disposed along thesecond circuit path. For example, the second circuit path can include aserially disposed inductive element matched with the transducer forreducing a reactance along the second circuit path. Thus, a signalreceived at the transducer can be coupled more effectively to an inputof the receiver. In a specific application, an inductance of theserially disposed inductive element substantially matches an inductanceof the transducer.

Further, a reactance of components disposed along the second circuitpath can be matched to cancel a reactance of at least a portion of areactance of components along the first circuit path so that a reactanceof at least a portion of the overall circuit path is reduced.Accordingly, a transducer can be coupled to a receiver input via acircuit path that is less susceptible to noise.

Prior to transmitting, a combined reactance along the first circuit pathincluding the transducer can be tuned to increase a magnetic poweroutput of the transducer at a particular carrier frequency.

Another aspect of the present invention concerns tuning a transducer forincreased reception or transmission. For example, a second transducercan be positioned to receive a portion of the magnetic signaltransmitted from a first transducer. While driving the first transducervia a connection through the first circuit path, an impedance along thefirst circuit path can be adjusted so that an increased signal isreceived at the second transducer. Alternatively, an impedance along thesecond circuit path can be adjusted for increased reception of amagnetic signal. For example, a transducer can be coupled to receiveover the second circuit path while a signal is received from a secondtransducer. During reception, the transducer and related circuitry alongthe second circuit can be tuned for increased reception of the receivedsignal. Accordingly, a single transducer can be tuned for optimallyreceiving or transmitting.

One of multiple transducers can be selected and an impedance along acorresponding circuit path can be adjusted to respectively transmit orreceive. In one application, the multiple transducers are orthogonallydisposed with respect to each other.

Another aspect of the present invention involves tuning the transducerwith a capacitance in parallel with the transducer. For example, acapacitance can be disposed along a circuit path in parallel with thetransducer for efficient tuning.

The previously discussed aspects of the present invention haveadvantages over the prior art. For example, one application of thepresent invention involves utilizing a relatively small transducer ormultiple transducers for transmitting and receiving wirelessinformation. In this instance, a hands-free headset or transceiverdevice supporting transmitting and receiving wireless audio datainformation can include minimal components such as a speaker,microphone, battery pack, processor circuitry and a transducer device.The size and weight of the transducer device for transmitting andreceiving wireless signals can be significantly reduced because a singletransducer (potentially one of multiple selectively activatedtransducers) can be tuned for both transmitting and receiving. Thus, theoverall size and weight of the transducer system can be reduced so thata hands-free headset can be more comfortably worn by a user.

In one application, a hands-free headset is so small that it is easilyclipped or secured to an ear. In such an application, size and weight ofthe transceiver more significantly affects whether the headset devicecan be comfortably worn by a user.

Based on other principles of the present invention, a transducer devicecan be dynamically adjusted for transmitting and receiving over anoptimal carrier frequency. For instance, one or multiple transceiverdevices can be dynamically adjusted in the field to optimize use of anavailable wireless spectrum. Interference can be reduced among multipletransceivers in the same general vicinity by dynamically tuningcorresponding transducers for receiving and transmitting over differentcarrier frequencies. Dynamic tuning of a transducer device typically canbe achieved in a relatively short period of time when electronicswitches are provided to adjust corresponding circuitry coupled withrespective transducers.

Previously, a single transducer was typically employed to transmit awireless signal while another transducer was employed to receive awireless signal at a fixed frequency. As mentioned, employing individualtransducers in this manner to transmit and receive can be costly interms of size and weight.

Dynamic tuning of one or multiple transducer devices according to theprinciples of the present invention has other benefits. For example, atransducer device can be optimally tuned in the field for transmittingand receiving at a particular carrier frequency and bandwidth. Whenproperly tuned, a wireless link is generally more reliable. That is,attempted data transmissions are more likely to be received at a targetdevice. In a bi-directional audio communication device, it is thereforeless likely that a user will have to repeat a verbal message due to lostdata. Yet another benefit of the present invention relates to batterylife. Dynamic tuning of a transducer device in a particular environmentcan ensure that a significant portion of energy dissipated by thetransducer and related circuit is directed towards generating a wirelesssignal such as a magnetic field rather than being needlessly dissipatedby related circuitry. In other words, the energy expended per bit ofdata transmitted to a target device can be optimized or minimized for aparticular application. As a result, the effective energy spent fortransmitting a wireless signal can be minimized and a correspondingbattery powering the transceiver device typically can last longer. Thisis especially advantageous in applications in which the transceiverdevice is powered by coin-sized batteries and must transmit significantamounts of data to a remote target transceiver device.

According to other aspects of the present invention, electroniccircuitry can be shared among multiple transducer devices fortransmitting and receiving wireless data signals. For example, anelectronic circuit for transmitting and receiving can be switched amongmultiple transducers, each of which has unique electroniccharacteristics that effect tuning. A dynamically tuned circuit canprovide a range of tuning capability so that each of multiple uniquetransducers can be optimally tuned for transmitting or receiving. Thus,component variations in the transducer devices can be dynamicallycompensated in the field on short order.

In one application, a transducer device is tuned based upon feedback bya receiving transducer. More specifically, a transducer in thetransceiver device can generate a wireless signal while anothertransducer in the same transceiver device can monitor the generatedsignal. Accordingly, a transducer can be dynamically tuned in the fieldfor receiving or transmitting based on feedback from another transducerlocated within the same transceiver device. Again, energy is notneedlessly wasted while generating a wireless signal to a remote targetdevice.

Characteristics of electronic components can decay over time. Since suchcomponents are typically selected to tune a transducer device fortransmitting or receiving, a carrier frequency over which a transceiverdevice is set to transceive, e.g., transmit or receive, can vary as aresult of a component's changing electronic characteristics. Forexample, a capacitance of an electronic component for tuning atransducer to a specific carrier frequency can change under certainenvironmental conditions such as extreme temperature or humidity. Thiscan result in a shift in a resonant frequency and less efficientcoupling between two transceiver devices. According to the principles ofthe present invention, a transducer device can be dynamically tuned tocompensate for aging, temperature or other environmental conditions foroptimally transmitting or receiving a wireless signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a block diagram illustrating a transceiver system according tocertain principles of the present invention.

FIG. 2 is a block diagram of a transducer and related circuitry fortransmitting and receiving according to certain principles of thepresent invention.

FIG. 3 is a circuit diagram including an adjustable varactor capacitorin which a transducer is tuned for receiving according to certainprinciples of the present invention.

FIG. 4 is a flow chart illustrating a method for adjusting a varactorcapacitor and tuning a transducer for receiving according to certainprinciples of the present invention.

FIG. 5 is a circuit diagram including an adjustable varactor capacitorin which a transducer is tuned for transmitting according to certainprinciples of the present invention.

FIG. 6 is a flow chart illustrating a method for adjusting a varactorcapacitor for transmitting over a transducer according to certainprinciples of the present invention.

FIG. 7 is a circuit including an adjustable transducer according tocertain principles of the present invention.

FIG. 8 is a flow chart illustrating a method for adjusting a variableinductor transducer for transmitting according to certain principles ofthe present invention.

FIG. 9 is a circuit diagram including a capacitor bank for tuning atransducer device according to certain principles of the presentinvention.

FIG. 10 is a flow chart illustrating a method for adjusting acapacitance provided by a capacitor bank that tunes a transducer fortransmitting according to certain principles of the present invention.

FIG. 11 is a circuit diagram including a first transducer fortransmitting a wireless signal and second transducer for receiving awireless signal according to certain principles of the presentinvention.

FIG. 12 is a flow chart illustrating a method for tuning a transduceraccording to certain principles of the present invention.

FIG. 13 is a circuit diagram of a transceiver system including multipletransducers for transmitting and receiving wireless signals according tocertain principles of the present invention.

FIG. 14 is a flow chart illustrating a method for tuning a transducerfor transmitting or receiving according to certain principles of thepresent invention.

FIG. 15 is a circuit diagram for tuning a transducer for receivingaccording to certain principles of the present invention.

FIG. 16 is a circuit diagram for tuning one of multiple transducersaccording to certain principles of the present invention.

FIG. 17 is a circuit diagram for transmitting and receiving over one ofmultiple transducers according to certain principles of the presentinvention.

FIG. 18 is a circuit diagram for tuning one of multiple transducersaccording to certain principles of the present invention.

FIG. 19 is a diagram of a capacitor bank according to certain principlesof the present invention.

FIG. 20 is a block diagram illustrating a wireless system for two-waycommunications according to certain principles of the present invention.

FIG. 21 is a circuit diagram illustrating a transceiver system fortransmitting and receiving a wireless signal over a single transduceraccording to certain principles of the present invention.

FIG. 22 is a circuit diagram illustrating yet another transceiver systemfor transmitting and receiving a wireless signal over a singletransducer according to the principles of the present invention.

FIG. 23 is a detailed circuit diagram illustrating a transceiver systemfor transmitting and receiving a wireless signal according to certainprinciples of the present invention.

FIG. 24 is a detailed circuit diagram illustrating a transceiver systemaccording to certain principles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A description of preferred embodiments of the invention follows.

FIG. 1 is a block diagram illustrating a transceiver system according tocertain principles of the present invention. As shown, a firsttransceiver 114 is coupled via an inductive or magnetic field to secondtransceiver 165. First transceiver 114 is optionally portable so thatits orientation is not fixed with respect to second transceiver 165,which includes control circuit 161 and transducer 163. Secondtransceiver 165 itself can be portable while first transceiver is afixed. Further, first transceiver 114 and second transceiver 165 bothcan be portable so that they are mobile and oriented in any manner withrespect to each other.

Additional details of transceiver devices and methods of communicatingare discussed in pending U.S. application Ser. No. 09/053,107 filed onApr. 1, 1998, the entire teachings of which are incorporated herein bythis reference.

Generally, tuning circuit 144 and related circuitry is controlled byprocessor 142 to transmit over transducer 113 while tuning circuit 146is controlled by processor 142 to receive over transducer 113. Tuninginformation can be stored in memory 140 and retrieved by processor 142for setting corresponding circuitry.

More specific details of transceiving (transmitting and/or receiving)wireless signals according to the principles of the present inventionare discussed relative to the following figures.

FIG. 2 is a block diagram illustrating a transducer for transmitting andreceiving wireless signals according to certain principles of thepresent invention. As shown, a single transducer 113 can be employed toreceive and transmit time-multiplexed wireless signals such as encodedmagnetic fields.

One aspect of the present invention involves transmitting and receivinga wireless signal such as a magnetic field over transducer 113. In aspecific embodiment, a single transducer 113 can be tuned via impedancenetwork 110 for transmitting and receiving at different times. Forexample, transducer 113 can be tuned to receive for a specified durationof time, while at other times, transducer 113 can be tuned to transmitfor a duration of time. Accordingly, a single transducer can supportbi-directional communications with one or multiple remote transceivers.The use of a single transducer supporting bi-directional communicationscan be particularly advantageous in space restricted applications.

As previously discussed, transducer 113 can be an inductive device forgenerating a wireless signal such as a magnetic field. In such anapplication, transducer 113 can be a coiled strand of wire. A magneticfield can be generated when a current is driven through the coiled wire.A ferrite rod can be disposed at a core of the coiled strand of wire toenhance directional or signal strength characteristics of transducer 113for receiving and transmitting a magnetic field. In a specificapplication, transducer 113 includes a 3×25 mm (millimeters) ferrite rodhaving eight turns of wire. However, specific attributes of transducer113 can vary depending on a particular application.

As shown, network 110 includes capacitor C111, resistor R112, transducer113, capacitor C114, inductor L115, and capacitor C116. Although FIG. 1illustrates a specific network configuration including multipleelectronic circuit elements for tuning transducer 113, network 110 canbe modified while still achieving the principles of the presentinvention.

In other words, functional aspects of the circuit as shown in FIGS. 1and 2 can be achieved using other circuit configurations. For example,capacitors C106 and C116 can be combined into one capacitor.

In practice, resistor R112 is a model for the parasitic resistance oftransducer 113. The value of R112 can be dynamically controlled tochange the operating efficiency, Q. For example, R112 can be adjusted tochange an effective bandwidth at which a tuned transducer transmits orreceives a wireless signal. This can be achieved by switching additionalresistors in parallel with R112.

Consequently, a transducer device can be tuned in two ways. First, atransducer can be tuned to transmit or receive over a wider or narrowerbandwidth centered around a resonant frequency. Also, a transducer canbe dynamically tuned to efficiently transmit or receive at a selectedresonant frequency.

In one application, a transducer is tuned to receive over a widebandwidth while it is otherwise tuned to transmit over a narrowerbandwidth. Such a transducer receiving over a wider bandwidth canpotentially receive wireless signals from multiple transceiver devicestransmitting at different resonant frequencies without having to re-tunethe transducer to each of the different resonant frequencies.

Transceiver 100 typically includes circuitry for transmitting andreceiving over transducer 113. For example, transceiver 100 can includetransmitter amplifier 102, switch S104, switch S105, capacitor C106, andreceiver amplifier 108. In a transmit mode, switch S104 and switch S105are both switched to the ‘T’ position and transmitter 102 drivestransducer 113 and related circuitry as shown in FIG. 1. Receivercircuit including L115, C116, C106, and receiver amplifier 108 aregenerally disconnected (via open switch S105) from transmitter circuitincluding amplifier 102, S104, C111, C114, R112 and transducer 113 whilein a transmit mode.

Switches S104 and S105 can be electronically controlled BJT (BipolarJunction Transistor) or FET (Field Effect Transistor) devices. When suchdevices are used, fast switching times can be achieved and transducer113 can be quickly tuned to either transmit or receive. Consequently, ahalf duplex system including transducer 113 can be switched so fast thatthe system of the present invention appears to support full-duplexcommunications.

Other types of switches including mechanical devices such as relays,solenoids, and the like also can be used to switch between transmittingand receiving according to the principles of the present invention.

As shown in FIG. 2, switches S104 and S105 are switched to the ‘T’position for transmitting. In a receive mode, S104 and S105 are bothgenerally switched to position ‘R’ and receiver 108 receives a signalsensed by transducer 113. Typically, switches S104 and S105 are drivenby another electronic device controlled by, for example, amicroprocessor that selects either transmitting or receiving.

Receiver 108 can be an amplifier device that senses a relatively smallAC (Alternating Current) signal and amplifies it for further processing.For example, an amplitude varying voltage as sensed by transducer 113can be amplified so that data such as digital information modulated ontoa selected carrier frequency can be further processed by amicroprocessor device. Receiver 108 can therefore be an amplifierdevice.

As discussed, one aspect of the present invention concerns tuningtransducer 113 for transmitting and receiving at different intervals oftime. In a transmit mode, a series LC circuit can be tuned to a selectedcarrier frequency so that the impedance of transducer 113 is effectivelyreduced. More specifically, an overall reactance (as seen by transmitter102) of combined circuitry C111, C114, R112, and transducer 113 can beeffectively reduced so that a majority of energy is coupled totransducer 113 to generate a magnetic field. A portion of total energywill be dissipated by series resistor R112. However, the energydissipated by R112 is typically minimal and depends on the efficiency,Q, of the circuit.

Since a portion of the transmitter circuitry, i.e., capacitor C111, isin series with transducer 113, its effects must be addressed while inthe receive mode. For example, the capacitive effects of C111 can benullified by inductive effects of inductor L115 when switches S104 andS105 are switched to receive mode.

During reception, a parallel LC circuit including transducer 113generally can be tuned for optimal reception of a wireless signal suchas a magnetic field. For example, receiver circuitry can be tuned toincrease an effective impedance of transducer 113 so that a relativelylarge voltage develops at amplifier 108 as a result of a receivedwireless signal. A voltage generated by transducer 113 during receptioncan be coupled to input of receiver amplifier 108, where the receivedsignal is further amplified and digitally processed.

In one application, an impedance such as a reactance along a receivercircuit path including C111, S105 and L115 between transducer 113 andreceiver 108 is reduced for better signal reception, i.e., the circuitcan be tuned to achieve a higher signal-to-noise ratio at receiveramplifier 108. For example, inductor L115 can be impedance matched tocapacitor C111 so that capacitors C116, C114, C106, and serialcombination of R112 and transducer 113 form a parallel tunable LC tankcircuit. A substantial reactance of C111 and L115 can cancel each otherwhile switched to a receive mode. As a result, C114 can be effectivelyin parallel with C106 and C116 via a low impedance path including C111,S105 and L115.

In a transmit mode, C111 and C114 are provided to tune transducer 113.That is, a capacitance of C111 and C114 can be adjusted to cancel theinductive effects of transducer 113. A ratio of C111 to C114 istypically selected to set a peak current driving transducer 113.

Both C114 and C106 can be tunable capacitors for adjusting the resonantfrequency of corresponding transmit and receive circuits. Consequently,capacitors C114 and C106 can be electrically or mechanically tuned sothat the corresponding circuit resonates at a particular carrierfrequency.

Transceiver device 112 can be tested at a factory to determine optimalsettings for capacitors C106 and C114 for transmitting and receiving ata particular carrier frequency. Either or both capacitors C106 and C114can be fixed to permanent values in the factory. In one application,C106 and C114 are set or adjusted to a value during an assembly andtesting process of a transceiver device and switches S104 and S105 arethereafter used to select a mode of transmitting or receiving.

Alternatively, information concerning capacitor selection can be storedin memory and later retrieved to dynamically tune transducer 113 in thefield depending on a particular application. More specifically, switchsettings can be stored in a table and applied to select a capacitance ofa particular capacitor bank to tune transducer 113 for transmitting orreceiving at a particular carrier frequency. Information stored inmemory can include binary data identifying which of multiple switches ina capacitor bank will be activated to select a particular capacitance ofC106 or C114.

During transmission, transmitter amplifier 102 generates a voltage thatcouples across resistor R112 and transducer 113. In one embodiment,transmitter 102 generates an output at one of two voltages from anelectronic device such as an ASIC (Application Specific IntegratedCircuit). For example, transmitter 102 can be designed to drive a binaryvoltage output of either 0 volts or 2 volts. By varying the voltageoutput at transmitter 102 at different frequencies or for differentdurations of time, data information such as binary encoded data can bemodulated onto a carrier frequency and transmitted over transducer 113.Thus, a digital integrated circuit device can be used to drivetransducer 113.

As an alternative to a binary voltage output at transmitter 102, anyother suitable voltage such as an analog sinusoidal voltage or otheramplitude varying analog voltage can be used to effectively drivetransducer 113 and related circuitry. Regardless of voltage type, awireless signal can be generated by transducer 113 for coupling to oneor multiple target devices.

In one application, transducer 113 is tuned to transmit and receive at aresonant frequency of around 12.0 MHZ. However, any other suitableresonant frequency generally can be used.

As previously discussed, capacitor C106 and C114 as well as othercomponents shown in FIG. 2 can be adjustable to provide tuning oftransducer 113 for either transmitting or receiving.

In one embodiment, an adjustable capacitor is formed via a bank ofparallel capacitors C1110 that are potentially connected to ground viacorresponding switches S1120 as shown in FIG. 19. To select a particularcapacitance for tuning transducer 113 for either transmitting orreceiving, switches such as FET devices are activated to connect an endof a corresponding capacitor to ground. When more capacitors incapacitor bank C1110 are connected to ground via corresponding switches,S1120, an effective capacitance of the bank increases. Conversely, anoverall capacitance supplied by the capacitor bank decreases ascapacitors are disconnected from ground via corresponding switches.Consequently, transducer 113 can be tuned to a particular resonantfrequency by adjusting a reactance of circuits via switching fortransmitting or receiving. As previously discussed, switch settinginformation can be stored as binary data in memory.

Referring again to FIG. 2, capacitor C116 can be selected to provide amajority of capacitance provided by combination of C106, C114 and C116.Thus, one or multiple capacitors comprising C106 can be componentshaving a smaller capacitance value to provide fine tuning of combinedcapacitance of C106 and C116. Likewise, C111 can be selected to providea majority of capacitance provided by combination of C111 and C114,while C114 itself can be a capacitor bank comprising many smallercapacitors for fine tuning. Note that C114 and C111 are set to controlthe maximum signal strength.

Another aspect of the present invention concerns selecting of componentsdisposed in either the transmit or receive circuit. Although anycomponent values generally can be selected for use in transceiver device112, component values are typically selected to provide a desiredperformance. In space restricted applications, an actual size ofcomponents is a factor to consider for selecting component values.Typically, capacitor values are on the order of micro-farads orpicoFarads. In other applications, power dissipation and signalbandwidth are factors to consider for properly selecting componentvalues. Thus, selection of components can differ depending on aparticular application.

In a specific application, transducer 113 is selected to have a maximumnumber of effective ampere-turns so that a predetermined amount of poweris dissipated in lumped loss element resistor R112. Typically, R112represents a majority of losses in the transmit path. Transmitter 102and each passive component has its own loss element but this isgenerally minimal.

Although 12 MHZ is a typical resonant frequency, for transmitting orreceiving a selected carrier frequency can be any suitable setting suchas between 0.5 and 60 MHZ.

As previously discussed, a reactance of the transmit circuitry includingC111, C114, R112 and transducer 113 can be reduced so that the circuithas only real impedance components. Thus, the resonant frequency, ω₀, isdefined by:$\omega_{o} = \frac{1}{\sqrt{L_{113}( {C\quad 111\text{❘❘}C\quad 114} )}}$Given a carrier frequency generally centered around 12.0 MHZ, transducer113 can be 1.5 μH while C111 and C114 can be respectively 33 pF(picoFarads) and 84.3 pF.

Efficiency factor, Q, of the circuit can be approximately 40 dependingon components selected resulting in resistance R112, inductance oftransducer 113 (noted above as L₁₁₃), and capacitor divider C111 andC114. For example, the efficiency Q can be defined as the energy storedby transducer 113 in its magnetic field divided by the energy dissipatedby the overall transmitter circuit. Using RMS (Root Mean Squared)voltages and currents, the following approximate equations reflectattributes of the circuit while in a transmit mode:$Q = {\frac{V_{113}}{V_{IN}}( \frac{{C\quad 111} + {C\quad 114}}{C\quad 111} )}$P _(R112)=(I ₁₁₃)² ·R112where

-   -   P_(R112)=power dissipated in resistor R112    -   Q=efficiency or quality factor of the circuit    -   V_(in)=output voltage of transmitter 102    -   V₁₁₃=voltage across transducer 113    -   F₀=resonant frequency        Typical values for the circuit are:    -   F₀=12 MHz    -   P_(R112)=25 mW (milliwatts)    -   Q=40    -   L₁₁₃=1.5 μH (microhemries)    -   C111=33 pF (picofarad)    -   C114=84.3 pF (picofarad)    -   R112=2.8 ohms    -   data throughput rate=204 kilobits/second    -   Bandwidth around carrier frequency=300 Kilohertz Approximate        range of transceiver=1.5 meters

One factor to consider when selecting a transducer 113 impedance iselectric field coupling between a remote transmitter and transducer 113.For example, if the impedance of transducer 113 is too high, it producessignals as a result of electric field coupling (with remote transducers)rather than or in addition to magnetic field coupling. Typically, theinductance of transducer 113 is selected to substantially supportinductive coupling. Thus, continuous coupling can be supported betweentransducer 113 and a remote device without nulls as sometimesexperienced with RF devices.

Component values for capacitors are generally selected so they arelarger than the parasitic capacitance of the circuit board andcorresponding traces, including parasitic output capacitance oftransmitter 102 and input capacitance of receiver 108 potentiallydisposed in an electronic device such as an ASIC (Application SpecificIntegrated Circuit).

As previously discussed, a component value of inductor L115 is selectedto cancel capacitive effects of C111. When L115 is properly selected, alow impedance path is generally created so that C114, C116 and C106 areeffectively in parallel with each other and transducer 113.

FIG. 3 is a circuit diagram including an adjustable varactor capacitorin which a transducer is tuned for receiving according to certainprinciples of the present invention. In addition to components as shownin FIG. 2, FIG. 3 includes adjustable varactor capacitor VC106 (in lieuof C106), bias generator 110, resistor R118 and capacitor C120.

Transducer 113 can be tuned for receiving based upon adjustments tovaractor capacitor VC106.

As previously discussed, receiver amplifier 108 can be coupled forreceiving over transducer 113 by setting switches S105 and S104 toposition ‘R’. While in the receive mode, an inductance of inductor L115approximately cancels a reactance of capacitor C111 for effectivelyconnecting transducer 113 via a low impedance path to capacitor C116 andvaractor capacitor VC106 through resistor R112. Varactor capacitorVC106, capacitor C116, capacitor C114 and transducer 113 form a paralleltunable LC tank circuit in which varactor capacitor VC106 is tuned toincrease reception of a wireless signal as detected at the input ofreceiver amplifier 108.

Bias generator 110 generates a voltage that is applied to VC106 throughresistor R118. The voltage of bias generator 110 is adjusted to select acapacitance of VC106. Consequently, transducer 113 and related circuitrycan be tuned to receive a wireless signal at a particular carrierfrequency.

Resistor 118 provides resistive isolation between bias generator 110 andthe received signal while capacitor C120 provides DC (Direct Current)isolation between bias generator 110 and receiver amplifier 108.

Although bias generator 110 can be controlled by many types of devices,bias generator 110 is typically a voltage source controlled by amicroprocessor and related circuitry to adjust characteristics of thecircuit and tune transducer 113 to receive at a particular carrierfrequency.

FIG. 4 is a flow chart illustrating a method for adjusting a varactorcapacitor and tuning a transducer for receiving according to certainprinciples of the present invention.

In step 310, transducer 113 is coupled to receiver amplifier 108 bysetting switch S105 to position ‘R’.

In step 320, transmitter amplifier 102 is decoupled from transducer 113by setting switch S104 to position ‘R’.

In step 330, a wireless signal is received over transducer 113.

In step 340, the signal at input or output of receiver 108 is measured.

In step 350, the capacitance of varactor capacitor VC 106 is adjustedvia the voltage supplied by generator 110 to increase or maximize thereceived signal strength at the input of receiver amplifier 108.

Generally, this same procedure can be utilized to set the transceiverdevice 112 in FIG. 2 for receiving. In this instance, capacitor C106 andC114 are adjusted for receiving at a particular carrier frequency.

FIG. 5 is a circuit diagram including an adjustable varactor capacitorin which a transducer is tuned for transmitting according to certainprinciples of the present invention. Generally, the circuit in FIG. 5 issimilar to that shown in FIG. 3 except varactor capacitor VC114,inductor L117, and capacitor C120 are provided to adjust characteristicsof the circuit for transmitting over transducer 113.

During operation and as shown in FIG. 5, transmitter amplifier 102 isswitched for transmitting over transducer 113 by setting switch S104 toposition ‘T’ while receiver amplifier 108 is decoupled from transducer113 and related circuitry by setting switch S105 to position ‘T’.

Capacitor C111, varactor capacitor VC114 and transducer 113 generallyform a tunable LC circuit while in the transmit mode. Typically,varactor capacitor VC106 is adjusted to increase or maximize a transmitsignal strength as measured at a magnetic loop probe located inproximity to transducer 113.

A voltage, Vs, is applied at inductor L117 as shown to select acapacitance of VC114. This voltage can be a DC voltage supplied from anysuitable electronic device or component such as a D/A(Digital-to-Analog) converter.

Although FIG. 5 illustrates a specific technique for providing a bias tonode V of VC114, other similar techniques can be utilized to select aneffective capacitance of VC114 for tuning the circuit.

Inductor L117 is typically provided to isolate voltage source Vs fromVC114 so that a signal supplied to transducer 113 is not effected byvoltage supply, Vs. Capacitor C120 is a blocking capacitor that isolatesDC (Direct Current) components of the voltage generated by voltagesource Vs from appearing across transducer 113.

FIG. 6 is a flow chart illustrating a method for adjusting a varactorcapacitor for transmitting over a transducer according to certainprinciples of the present invention.

In step 510, transducer 113 is coupled to transmitter 102 by settingswitch S104 to position ‘T’.

In step 520, receiver amplifier 108 is decoupled from transducer 113 bysetting switch S105 to position ‘T’.

In step 525, a signal is generated at transmitter 102 to transmit awireless signal over transducer 113.

In step 527, the generated wireless signal is measured to determine amagnetic field strength.

In step 530, the capacitance of varactor capacitor VC114 is adjusted viaa voltage supplied by source Vs to increase or maximize the transmittedsignal from transducer 113. A magnetic loop probe can be located inproximity to transducer 113 for monitoring a corresponding generatedmagnetic field. For example, a range of voltages can be applied tovaractor capacitor VC114 to determine which of multiple potentialsettings is preferred for transmitting data information at a particularcarrier frequency. FIG. 7 is a circuit including an adjustabletransducer device according to certain principles of the presentinvention. Generally, adjustable transducer 213 is tuned fortransmitting at a particular carrier frequency. Capacitor C114 can befixed instead of being adjustable as illustrated in previous figures.

To operate in a transmit mode, transmitter amplifier 102 is coupled totransducer 213 by setting switch S104 to position ‘T’ while receiveramplifier 108 is decoupled from variable inductor transducer 213 bysetting switch S105 to position ‘T’. While in this mode, capacitor C111,fixed capacitor C114 and variable inductor antenna 113 generally form atunable LC tank circuit.

Variable inductor transducer 213 can be adjusted to maximize or increasea magnetic field generated by transducer 213. For instance, transducer213 can be adjusted while a monitor such as a magnetic loop probelocated in proximity to transducer 213 monitors a wireless signalgenerated by transducer 213 to determine which of multiple potentialsettings is optimal for transmitting over adjustable transducer 213.

Depending on the application, an inductance value of adjustabletransducer 213 can be varied manually or automatically.

FIG. 8 is a flow chart illustrating a method for adjusting a variableinductor transducer for transmitting according to certain principles ofthe present invention.

In step 710, transducer 213 is coupled to transmitter 102 by settingswitch S104 to position ‘T’.

In step 720, receiver amplifier 108 is decoupled from transducer 113 bysetting switch S105 to position ‘T’.

In step 725, a signal is generated at transmitter 102 to transmit awireless signal over transducer 213.

In step 727, the generated wireless signal is measured to determine amagnetic field strength.

In step 730, the inductance of transducer 213 is adjusted to increase ormaximize the wireless signal generated by transducer 213. A magneticloop probe can be located in proximity to transducer 213 for monitoringa corresponding generated magnetic field. For example, transducer 213can be adjusted while the magnetic field is monitored to determine whichof multiple potential settings is preferred for transmitting datainformation at a particular carrier frequency.

FIG. 9 is a circuit diagram including a capacitor bank for tuning atransducer device according to certain principles of the presentinvention. As shown, this circuit illustrates an embodiment includingcapacitors C114A . . . C114N and corresponding switches S120A . . .S120N for tuning transducer 113.

To operate in a transmit mode, transmitter amplifier 102 is coupled totransducer 113 by setting switch S104 in position ‘T’ while receiveramplifier 108 is decoupled from transducer 113 by setting switch S105 inthe ‘T’ position. Capacitors 114A . . . 114N form a capacitor bank andswitches S120A . . . S120N form a switch bank that connect correspondingcapacitors C114 to ground.

When a switch S120 is closed, i.e., a low impedance path is providedbetween a corresponding capacitor and ground. An effective capacitanceof the capacitor is then imparted at node P to increase the overallcapacitance at node P. Conversely, when a switch S120 is open, i.e., ahigh impedance path is provided between a corresponding capacitor andground, a corresponding capacitor C114 is effectively removed from thecircuit so that this extra capacitance is no longer imparted at node P.

In one embodiment, switches S120 are FET (Field Effect Transistor) orBJT (Bipolar Junction Transistor) transistor devices controlled by amicroprocessor device. However, any type of mechanical or electronicswitch can be used.

Capacitor C111, selected capacitors C114 (those coupled to ground viaswitches S120) and transducer 113 form a tunable LC tank circuit.Capacitors C114A . . . C114N are switched into and out of the circuit tomaximize or increase a magnetic signal generated by transducer 113. Forexample, capacitor bank C114A . . . C114N can be adjusted while amonitor such as a magnetic loop probe located in proximity to transducer113 monitors a signal generated by transducer 113 to determine which ofmultiple potential settings is optimal for transmitting.

FIG. 10 is a flow chart illustrating a method for adjusting acapacitance provided by a capacitor bank that tunes a transducer fortransmitting according to certain principles of the present invention.

In step 910, transducer 113 is coupled to transmitter 102 by settingswitch S104 to position ‘T’.

In step 920, receiver amplifier 108 is decoupled from transducer 113 bysetting switch S105 to position ‘T’.

In step 925, a signal is generated at transmitter 102 to transmit awireless signal over transducer 113.

In step 927, the generated wireless signal is measured to determine amagnetic field strength.

In step 930, the capacitance provided by capacitor bank C114 is adjustedvia switches S120 to increase, maximize or optimize a magnetic signaltransmitted from transducer 113 for a particular application. A magneticloop probe can be located in proximity to transducer 113 for monitoringa corresponding generated magnetic field. For example, a capacitance atnode P can be adjusted while a magnetic field generated by transducer113 is monitored. Consequently, settings for the circuit in FIG. 8 canbe optimized for transmitting data information at a particular carrierfrequency. These settings as discussed can be learned and then stored inmemory.

FIG. 11 is a circuit diagram including transducers for transmitting awireless signal and a transducer for receiving a wireless signalaccording to certain principles of the present invention. Althoughswitch S105 can include multiple positions for coupling receiver 108 toeither transducer X, transducer Y, transducer Z or loop 119 forreceiving, receiver circuitry including S105, L115, C116, C106 andreceiver 108 can be duplicated for each of the transducers or wire loop119 so that a magnetic signal can be received over a single selectedtransducer or multiple transducers simultaneously.

As shown, second transducer 119 can be positioned for receiving awireless signal transmitted over transducer X, Y or Z, all of which aredisposed in a single transceiver device. In one application, transducer119 is a wire loop antenna that enables self-tuning of a selectedtransducer based upon feedback. For example, transducer 113 can be tunedto transmit a wireless signal based on signal strength of the wirelesssignal as received at second transducer 119.

Typically, transducer 119 or transducer 113 is fabricated from wireloops, coiled wires, wires, circuit board traces, discreet components,hybrid integrated circuit packages or monolithically integrated portionsof integrated circuits. Any suitable transducer device can be employedfor transmitting and receiving according to the principles of thepresent invention.

Generally, the circuit as shown in FIG. 11 operates based upon theprinciples as previously discussed. However, switch S105 can includeswitch position settings XR, YR, and ZR as shown for respectivelycoupling a respective transducer X (transducer 113), Y or Z and relatedcircuitry to an input of receiver 108. Circuit 1050 and circuit 1060respectively include transducer Y and transducer Z and related circuitrythat can be coupled to receiver 108. Note that each transducer can bedriven by a corresponding transmitter device as shown. Alternatively,switch S104 can be modified to include multiple switch positions so thattransmitter 102 can drive a selected transducer.

Switch position ‘L’ of switch S105 renders it possible to coupletransducer 119 to the input of receiver 108. Thus, a magnetic signal astransmitted by transducer X, Y or Z can be monitored based on thewireless signal as received at transducer 119.

Feedback provided by transducer 119 can be used to tune transducer 113.For example, capacitor C114 can be adjusted so that a maximal orincreased magnetic field is generated by transducer 113 based onfeedback from transducer 119.

Depending on characteristics or type of transducer 119, the circuit asshown can be modified for properly receiving a corresponding wirelesssignal at receiver 108.

As discussed, circuit 1050 and circuit 1060 each can include atransducer similar to transducer 113 and corresponding circuitry fortuning. For example, circuit 1050 and circuit 1060 each can include atransducer device similar to transducer 113. Also, each circuit 1050 andcircuit 1060 can include corresponding components such as R112, C114,and C111, similar to the circuitry shown for transducer 113.

Based upon switching of switch S105, a corresponding transducer can becoupled via circuit path including L115, C116 and C106 to the input ofreceiver 108. Capacitor C106 can be adjusted for tuning a transducer forreceiving a wireless signal. Thus, a single receiver 108 and relatedcircuitry can be adjusted or tuned to receive a wireless signal over aselected one of multiple transducers. Also, transducer X, Y or Z can beadjusted for transmitting a corresponding wireless signal. In oneapplication, transducers X, Y and Z are uniquely positioned so that theyare orthogonal to each other.

Transmitter amplifier 102 can be coupled to transducer 113 by settingswitch S104 to position ‘T’ while transmitter amplifiers in circuits1050 and 1060 are decoupled from their associated transducer Y and Z bysetting their corresponding switches to an open position.

Receiver 108 is coupled to transducer 119 by setting switch S105 toposition ‘L’. However, after an optimal setting is identified fortransmitting over a particular transducer, switch S105 can be switchedto receive on one of the other transducers. Thus, receiver 108 also canbe switched to receive a wireless signal from a remotely located source.

A combination of capacitor C111, capacitor C114 and transducer 113 forma tunable LC circuit, in which capacitor C114 is tuned to maximize orincrease the magnetic signal strength as generated by transducer 113.Transducer 119 is typically positioned in reasonable proximity such aswithin centimeters or millimeters of transducer 113 for receiving thecorresponding wireless signal generated by transducer 113. The strengthof the received wireless signal can be measured at the output ofreceiver amplifier 108. This feedback process also can be used to tunetransducer Y or transducer Z when switches are set to YT or ZTrespectively.

In one embodiment, each transducer device is uniquely positioned withrespect to each other. For example, three transducers such astransducers X, Y, and Z can be orthogonally disposed to each other alongan X, Y and Z axis for transmitting and receiving one or multiplewireless signals. Based upon this configuration, a continuous wirelesslink can be supported with a remote target device such as that shown inFIG. 1, even though an orientation of transducers changes as a result ofmotion.

FIG. 12 is a flow chart illustrating a method for tuning a transduceraccording to certain principles of the present invention.

In step 1110, transducer 113 is coupled to transmitter amplifier 102 bysetting switch S104 to position ‘XT’.

In step 1120, receiver amplifier 108 is coupled to transducer 119 bysetting switch S105 to position ‘L’. Transducer 119 can be tuned toreceive at the same carrier frequency as the magnetic field transmittedby transducer 113. This can be achieved by adjusting capacitance ofC116.

In one application, transducer 119 is tested at a factory and preferredcapacitance settings for each of multiple carrier frequencies arerecorded in memory for later use. For example, transducer 119 is exposedto a wireless signal having a known carrier frequency and capacitanceC106 is adjusted so that a maximal signal is received at receiver 108.Thus, transducer 119 can thereafter be tuned for optimally receiving awireless signal at the carrier frequency based on capacitor settings asstored in memory.

In step 1122, a wireless signal is transmitted over transducer 113.

In step 1124, part of this transmitted signal is received overtransducer 119.

In step 1126, the wireless signal as received over transducer 119 ismeasured at receiver 108.

In step 1130, capacitor C114 is adjusted so that an increased or maximalsignal as generated by transducer 113 is received at the input ofreceiver amplifier 108 for a particular carrier frequency.

The strength of the wireless signal generated by transducer 113 asreceived at receiver 108 can be measured for tuning transducer 113. Forexample, the voltage level of the received signal at receiver 108 canindicate a relative signal strength of the received magnetic fieldgenerated by transducer 113. Other methods of measuring the power levelof the wireless signal also can be employed to provide a relativemeasure of received signal strength.

Based on a power level of the received magnetic field at transducer 119,transducer 113 can be tuned to transmit an increased signal. In otherwords, capacitor C114 can be swept through a range of potentialcapacitance settings so that an optimal setting can be identified for aparticular environment in which the transceiver device operates.Accordingly, settings can be learned and stored in memory for later use.

FIG. 13 is a circuit diagram of a transceiver system including multipletransducers for transmitting and receiving wireless signals according tocertain principles of the present invention. As shown, switch S105 canbe set to receive over either transducer X (transducer 113), transducerY or transducer Z. Circuitry 150 for driving transducer 113 (transducerX) can be duplicated in circuits 1050 and 1060 for transmitting overtransducer Y or Z as previously discussed. Accordingly, one of multipletransducers in a transducer device can be selected for transmittingwhile a different transducer can be selected for receiving. Asdiscussed, one purpose for tuning a selected transducer is to increaseits generated field strength.

In a specific example, transmitter amplifier 102 is coupled to transmitover transducer 113 by setting switch S104 to position ‘XT’ while asecond transducer is selected via switch S105 to receive a wirelesssignal for tuning transducer 113. More specifically, switch S105 asshown is set to position ‘YR’ for receiving over transducer Y.Alternatively, switch S105 can be set to optional position T, thusdisconnecting receiver 108 from all transducers to reduce powerconsumption or circuit interference. For this discussion, assumereceiver 108 is coupled to receive over transducer Y and switch S104 isset to position ‘YR’ as shown.

As previously discussed, capacitor C111, capacitor C114 and transducer113 form a tunable LC circuit, in which capacitor C114 is tuned totransmit at an optimal signal strength. Generally, a magnetic signal canbe transmitted over transducer 113 while attributes of the transmittedmagnetic signal are received and monitored over transducer Y. Hence,transducer 113 can be tuned to optimally transmit based on feedbackreceived at transducer Y.

Conversely, a receiving transducer and related circuitry can be adjustedto optimally receive a signal that is transmitted by a selectedtransducer. For example, capacitor C106 can be adjusted to optimallyreceive a wireless signal as generated by transducer X.

Since coupling is based on induction, the orientation of a transducercan effect whether a signal is detected. If the transmitted magneticsignal does not couple to transducer Y due to its orientation, anothertransducer can be selected to monitor the wireless signal from thetransducer X. For example, switch S105 can be switched to receive overtransducer Z instead of transducer Y if no signal is detected. However,since transducers are typically located within less than several inchesfrom each other, coupling is very likely for all transducers even whenthe transducers are positioned substantially orthogonal to each other.

Based on the techniques as discussed, any one of multiple transducerscan be tuned for optimally transmitting or receiving during field use.That is, a transceiver device need not be returned to the factory fortesting and adjusting characteristics of the circuit. It can be adjustedduring normal operational use of the transceiver device. Thus, atransceiver device incorporating the principles of the present inventioncan adapt itself to provide optimal, improved or continuous couplingwith a remote device despite operation of the device in an ever-changingenvironment. A power supply energizing the transceiver will last longerbecause the transceiver device is optimally linked to a target device.More specifically, circuits can be tuned so that minimal energy isdissipated while generating a maximum magnetic field.

FIG. 14 is a flow chart illustrating a method for tuning a transducerfor transmitting or receiving according to certain principles of thepresent invention.

In step 1310, transducer 113 is coupled to transmitter amplifier 102 bysetting switch S104 to position ‘XT’.

In step 1320, receiver amplifier 108 is coupled to transducer Y bysetting switch S105 to position ‘YR’. Typically, transducer YR is tunedto receive at the same carrier frequency as transmitted by transducer113. This can be achieved by adjusting capacitance at C106.

In step 1322, a wireless signal is transmitted over transducer X.

In step 1324, the transmitted signal from transducer X is received overtransducer Y.

In step 1326, the signal as received over transducer Y is measured atreceiver 108.

In step 1330, a capacitance provided by capacitor C114 is adjusted sothat an increased, optimal or maximal signal as generated by transducerX is received at the input of receiver amplifier 108 for a particularcarrier frequency.

In step 1340, a wireless signal is transmitted over transducer X.

In step 1350, a capacitance of C106 can be adjusted so that transducer Yand related circuitry is tuned for optimally receiving. For example,transducer Y and related circuitry are adjusted to optimally receive awireless signal transmitted by transducer X.

The strength of the wireless signal generated by transducer 113 asreceived at receiver 108 over transducer Y is optionally measured fortuning transducer 113 or transducer Y. For example, the voltage level ofthe received signal at receiver 108 can indicate a relative signalstrength of the received magnetic field generated by transducer 113.Other methods of measuring the power level of the wireless signal alsocan be employed to provide a relative measure of received signalstrength.

Based on the actual or estimated power level of the received magneticfield at transducer 119, transducer X, transducer Y, or transducer Z canbe selectively tuned to transmit or receive an increased magneticsignal. In one application, capacitor C114 or C106 can be swept througha range of potential capacitance settings to learn which setting isoptimal for transmitting or receiving over a corresponding transducer.

FIG. 15 is a circuit diagram for tuning a transducer for receivingaccording to certain principles of the present invention. As shown,transducer 118 is provided for generating a magnetic field that isreceived over selected transducer 113.

To adjust a transducer such as transducer X for receiving, receiveramplifier 108 of transceiver 100 is coupled to transducer 113 by settingswitch S105 to position ‘XR’ while transmitter amplifier 102 isdecoupled from transducer 113 by setting switch S104 to position ‘R’.Transmitter 117 is coupled to transducer 118 through capacitor 120 whenswitch S103 is set to position ‘T’.

Similar to the techniques as previously discussed, capacitor C106 can beadjusted to tune transducer 113 for receiving a wireless signalgenerated by transducer 118. Specifically, capacitor C106 can be sweptthrough a range of potential capacitance settings to determine whichsetting provides an optimal setting for receiving over transducer 113.

Switch S105 also can be switched to select a mode for receiving overtransducer Y or Z. Thus, transducer Y or Z can be optimally tuned forreceiving a wireless signal generated by transducer 118.

FIG. 16 is a circuit diagram for tuning one of multiple transducersaccording to certain principles of the present invention. As shown,separate circuits are provided for transmitting and receiving over acorresponding transducer. For example, circuit 185 is dedicated totransducer 113 for transmitting and receiving. Circuit 186 and circuit187 include similar components as shown for circuit 185. However,circuit 186 and 187 are employed to receive and transmit over transducerY of circuit 186 and transducer Z of circuit 187, respectively. In otherwords, circuit 185 can be replicated for transmitting and receiving overmultiple transducers.

Circuitry including receiver 108, switch S110, capacitor bank C4010 andswitch bank S4020 can be disposed so that they are common to allcircuits. For example, switch S110 can be switched to receive over oneof multiple transducers such as orthogonally positioned transducers X, Yand Z. As shown, receiver 108 is coupled to transducer Y. Since aportion of circuitry is shared among transducers, specific circuitrysuch as capacitor bank C4010, receiver 108 and switch bank S4020 are notneedlessly duplicated for each circuit.

In a transmit mode, switch S105 as well as complementary switchesdisposed in circuit 186 and circuit 187 can be set to position ‘T’ fordecoupling receiver 108 from a corresponding transducer.

Based upon this configuration, a single transducer or multipletransducers can be tuned and driven at the same time using a commoncarrier frequency or different carrier frequencies. In a receive mode, aselected one of multiple transducers can be individually tuned forreceiving a wireless signal via coupling provided by switch S110.

FIG. 17 is a circuit diagram for transmitting and receiving over one ofmultiple transducers according to certain principles of the presentinvention. As shown, minimal circuit components can be employed to tunea transducer for transmitting or receiving at a particular carrierfrequency.

Switch S105 selects which of multiple transducers such as transducer X,transducer Y (in circuit 196) or transducer Z (in circuit 197) will betuned for receiving at receiver 108. Common circuitry shared by themultiple transducers includes receiver 108, capacitor bank C4010, switchbank S4020, C116 and L115. Generally, the circuitry shown in circuit 195can be replicated in circuit 196 to receive/transmit over transducer Yand circuit 197 to receive/transmit over transducer Z.

To transmit over a particular transducer, switch S104 or its complementin circuit 196 or 197 is set to position ‘T’ while switch S105 is set toreceive over another transducer. For illustrative purposes, as shown inFIG. 17, transmitter 102 is coupled to drive transducer X while receiver108 is coupled to receive over transducer Y.

Based upon the circuit configuration as shown, a selected transducer canbe tuned for optimally transmitting or receiving a wireless signal. Thistechnique of adjusting each transducer via capacitance provided bycapacitor bank 4010 simplifies tuning multiple transducers, each ofwhich potentially has its own unique electronic characteristics. Forexample, electronic characteristics of transducer devices can vary fromcomponent to component as a result of manufacturing tolerances.Consequently, a single adjustable circuit can be adjusted to dynamicallytune each of multiple unique transducer devices for receiving ortransmitting.

FIG. 18 is a circuit diagram for tuning one of multiple transducersaccording to certain principles of the present invention. As shown,minimal circuit components can be employed to tune a selected transducerfor transmitting or receiving at a particular carrier frequency.Components in circuit 175 including C111, C114, R112 and transducer 113(transducer X) can be duplicated in circuit 176 and circuit 177. Circuit176 includes transducer Y while circuit 177 includes transducer Z.

Switch S105 can be switched to select which, if any, of multiplereceivers will be coupled to receiver 108 for receiving. As shown,switch S105 is set to position YP for receiving a wireless signal overtransducer Y.

In a similar manner, switch S104 can be switched to select which, ifany, of multiple transducers will be coupled to transmitter 102 fortransmitting.

Based on techniques as previously discussed, one transducer can be tunedfor transmitting while another transducer can be tuned for receiving.

FIG. 20 is a block diagram illustrating a wireless system for two-waycommunications according to certain principles of the present invention.The techniques as previously discussed can be used in this embodiment todynamically tune a transducer dedicated for either transmitting orreceiving.

As shown, transceiver device 2010 and transceiver device 2060communicate with each other via wireless signals. Each transceiverdevice can include at least one dedicated transmitter 2030, 2085(transducer and related circuitry) for transmitting a wireless signaland at least one dedicated receiver 2035, 2080 (transducer and relatedcircuitry) for receiving. A switch can be provided so that one ofmultiple uniquely oriented transducer devices within a transmitter orreceiver can be selected and dynamically tuned for transmitting orreceiving a wireless signal as previously discussed.

In a forward direction between transceiver 2010 and transceiver 2060,processor 2015 generates encoded data and transmits a wireless signalfrom transmitter 2030 at a selected carrier frequency. For example, adedicated transducer of transmitter 2030 can be dynamically tuned totransmit at a selected carrier frequency. Receiver 2080 is dynamicallytuned to receive at the selected carrier frequency and decode thereceived wireless signal at processor 2065.

In a reverse direction, processor 2065 generates encoded data andtransmits a wireless signal from transmitter 2085 at a dynamicallyselected carrier frequency. Receiver 2035 is dynamically tuned toreceive over the selected carrier frequency and decode the receivedwireless signal at processor 2015.

When full duplex communication is supported between transceiver 2010 and2060, a first carrier frequency can be utilized to transmit/receiveinformation in one direction while a different carrier frequency can beused to transmit/receive information in the opposite direction. Timedivision multiplexing techniques also can be used to transmit andreceive information over a commonly used carrier frequency.

Based on this configuration as shown in FIG. 20, a single dedicatedtransducer device can be dynamically or electronically tuned fortransmitting or receiving at a particular carrier frequency. In theevent that other wireless devices are utilizing a similar carrierfrequency, interference typically can be avoided during operational usein the field by dynamically tuning a transmitter/receiver pair of thetransducers to transmit and receive at another carrier frequency.

FIG. 21 is a circuit diagram illustrating a transceiver system fortransmitting and receiving a wireless signal over a single transduceraccording to certain principles of the present invention. As shown,certain circuit elements have been eliminated from the transceiversystem as shown in FIG. 2. More specifically, inductor L115 andcapacitors C106 and C116 have been eliminated.

The transceiver system as shown in FIG. 21 supports two-waycommunication over a single transducer device using fewer circuitcomponents. Consequently, the wireless communication system according tothe principles of the present invention can occupy a smaller volume andthus fit into yet smaller wireless transceiver devices.

To select a transmit mode, both switches S104 and S105 are set toposition T. Capacitor C114 is adjusted to tune transducer 113 fortransmitting at a selected carrier frequency similar to the circuits aspreviously discussed.

To select a receive mode, both switches S104 and S105 are set toposition R. Capacitor C114 is adjusted to tune transducer 113 forreceiving at a selected carrier frequency. A voltage proportional to areceived wireless signal at transducer 113 is generated at the nodeconnecting C111, C114 and R112. This generated voltage or signal iscoupled to receiver amplifier 108 through the circuit path includingswitch S105 and capacitor C111.

FIG. 22 is a circuit diagram illustrating yet another transceiver systemfor transmitting and receiving a wireless signal over a singletransducer according to certain principles of the present invention. Asshown, adjustable capacitor C114 and switch S104 have been eliminatedfrom the diagram as shown in FIG. 21. Also, capacitor C111 has beenmodified so that it is adjustable. In a addition to potentiallyoccupying yet a smaller volume, the circuit includes only one switchthat must be controlled for selecting either a transmit or receive mode.

To select a transmit mode, switch S105 is set to position T. In thisembodiment, capacitor C111 is adjusted to tune transducer 113 fortransmitting at a selected carrier frequency. Transmitter 102 iscontrolled to produce an output voltage and drive transducer 113.

To select a receive mode, switch S105 is set to position R and theoutput of transmitter 102 is driven to a virtual ground. When the end ofcapacitor C111 is switched to ground by setting the output oftransmitter 102, capacitor C111 is effectively disposed in parallel withthe combination of R112 and transducer 113. Similar to the principles aspreviously discussed, capacitor C111 is adjusted to tune transducer 113for receiving at a selected carrier frequency. During reception, avoltage proportional to a received wireless signal is generated at thenode connecting C111, R112 and S105. The generated voltage or signal iscoupled to receiver amplifier 108 through the low impedance circuit pathincluding switch S105.

FIG. 23 is a detailed circuit diagram illustrating a transceiver systemfor transmitting and receiving a wireless signal according to certainprinciples of the present invention. Generally, FIG. 23 is a moredetailed circuit diagram illustrating a system and method for providingan adjustable capacitance at C111 as shown in FIG. 22.

A capacitor bank including capacitor C230-1, C230-2, C230-3 . . . C230-nare selectively coupled to the output of transmitter 102 viacorresponding switches S240-1, S240-2, S240-3 . . . S240-n. Similar tothe principles as previously discussed, characteristics of the circuitare adjusted to tune transducer 113 for transmitting or receiving. Morespecifically, capacitors C230 are switched in and out to adjust acombined capacitance of C111 for transmitting or receiving a wirelesssignal over transducer 113.

FIG. 24 is a detailed circuit diagram illustrating a transceiver systemfor transmitting and receiving a wireless signal according to certainprinciples of the present invention.

As shown, C2410 is a DC blocking capacitor to keep DC voltages frominput of receiver 108. C2420 can be used to shift the resonant frequencyof the receiver (e.g., from 12 to 13 MHz) while R2430 can be adjusted tochange the Q of the receiver 108. This tuning circuit can ensure thatthe proper impedance is present at the frequency of use. This may benecessary due to variations in the coil impedance.

A variable capacitor C106 can be used for tuning the receiver. This canbe achieved in manufacturing by monitoring the received signal strengthand adjusting capacitor C106.

Automatic tuning of transducer 113 for receiving on receiver 108 can beachieved using a firmware driven capacitor table containing multipleprogrammable capacitors with 40 pF of range. This capacitor table can beloaded into memory when a transceiver system 2400 is turned on.

In one application, transceiver system 2400 is a TDD (Time DivisionDuplex) system that can be configured to alternately transmit andreceive in synchronization with a base transceiver unit. During atransmit frame, switch S105 is open and one or more of transmitterdrivers 102-1 . . . 102-n can be selectively activated (to control poweroutput levels) and to apply a 50% duty GMSK modulated square wave totransducer 113 and related circuitry. This front-end network, includingtransducer 113, and impedance scaling capacitors form a series tunedband pass filter that is centered at the carrier frequency. The resultis a GMSK modulated sine wave coil current.

During receive mode, a low impedance of the transmitter driver 102 canbe removed from the circuit. This can be accomplished by setting thedrivers to a high output impedance state. Switch S105 can be closed andthe receiver tuning network switches associated with C106 can beadjusted. In this mode, the series tuned band pass response of thetransmitter path has been converted into a purely parallel band passresponse.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A method for supporting inductive communication, the methodcomprising the steps of: coupling a transducer to a selected first orsecond circuit for either transmitting or receiving; adjustingelectrical characteristics of the first circuit to increase a magneticfield generated by the transducer; adjusting electrical characteristicsof the second circuit to increase a signal generated by the transducer.2. A method as in claim 1, wherein the characteristics of the first andsecond circuits are adjusted using passive circuit components.
 3. Amethod as in claim 1 further comprising the steps of: transmitting amagnetic field over the transducer when the transducer is coupled to thefirst circuit; and receiving a magnetic field over the transducer whenthe transducer is coupled to the second circuit.
 4. A method as in claim1 further comprising the step of: adjusting a capacitance of the firstcircuit to reduce an effective impedance of the transducer fortransmitting; and adjusting a capacitance of the second circuit toincrease an effective impedance of the transducer for receiving.
 5. Amethod as in claim 1 further comprising the step of: time divisionmultiplexing the transducer between the first and second circuits tosupport bidirectional communication with a transceiver at a remotelocation.
 6. A method as in claim 1, wherein the electricalcharacteristics of the first and second circuits are adjusted to achievean efficient coupling between either a transmitter or receiver.
 7. Amethod as in claim 1 further comprising the step of: adjusting areactance of the first circuit to transmit a magnetically encoded signalat a first carrier frequency and adjusting characteristics of the secondcircuit to receive a magnetically encoded signal at a second carrierfrequency.
 8. A method as in claim 1 further comprising the step of:disposing an inductive element in the second circuit, the inductiveelement having an approximate inductance as that of the transducer.
 9. Amethod as in claim 1, wherein the second circuit includes at least aportion of the first circuit that is coupled via a switch.
 10. A methodas in claim 1, wherein the first circuit serially tunes the transducerfor transmitting over the transducer and the second circuit paralleltunes the transducer for receiving over the transducer.
 11. A method forsupporting communication, the method comprising the steps of: switchingto select either transmitting or receiving over a transducer; via afirst circuit, effectively tuning the transducer to be a low impedancedevice for generating a magnetic field when a transmitter is switched totransmit over the transducer; via a second circuit, effectively tuningthe transducer to be a high impedance device for receiving a magneticfield when a receiver is switched to receive over the transducer.
 12. Amethod as in claim 11 wherein the first circuit is serially tuned fortransmitting over the transducer and the second circuit is paralleltuned for receiving over the transducer.
 13. A method as in claim 11further comprising the step of: in a transmitting mode, reducing anoverall reactance of the first circuit including the transducer bysubstantially matching an inductance of the transducer with acapacitance provided by the first circuit.
 14. A method as in claim 11further comprising the step of: via switching, decoupling thetransmitter from the first circuit and transducer, and coupling thereceiver and portion of the second circuit to the first circuit and thetransducer.
 15. A method as in claim 11 further comprising the step of:from the transmitter, generating an output at one of two voltages thatis coupled to drive the transducer.
 16. A method as in claim 11 furthercomprising the step of: disposing a resistance in series with thetransducer.
 17. A method as in claim 11 further comprising the step of:tuning a combined impedance of the first circuit and transducer formaximal magnetic power output of the transducer at a particular carrierfrequency.
 18. A method as in claim 11 further comprising the step of:adjusting an impedance of the first and second circuit to transmit andreceive over the transducer at a substantially similar carrierfrequency.
 19. A method as in claim 11 further comprising the step of:varying inductive characteristics of the transducer to adjust a combinedimpedance of the first circuit and transducer.
 20. A method as in claim11 further comprising the step of: adjusting a reactance of the first orsecond circuits by switching selected capacitors of a capacitor bank.